docs: def execute(self, fragment, pretty_format=True):
          """
          Run or aggregate a query fragment
  
          Concat the fragment to any stored fragments. If they form a complete
          query, run it and return the result. If not, store them and return
          None.
  
          """
          self.fragments = (self.fragments + "\n" + fragment).lstrip()
          try:
              line_parser.parseString(self.fragments)
          except ParseException:
              pass
          else:
              self.last_query = self.fragments.strip()
              self.fragments = ""
              return super(FragmentEngine, self).execute(self.last_query, pretty_format)
          return None